This invention relates to a conductive paste, particularly to a metallic paste for forming internal electrodes used in stacked ceramic capacitors.
A stacked ceramic capacitor is generally produced by blending a mixed ceramic powder with an organic binder, forming the resulting mixture into a sheet, and printing internal electrodes on the sheet using a conductive metallic paste, followed by stacking of such printed sheets, press bonding, cutting, sintering and formation of external electrodes which are connected to the internal electrodes. Such conductive metallic paste to be used for forming internal electrodes is prepared by blending metal powders such as of silver, palladium, etc. with a vehicle consisting of an organic binder and a solvent and kneading the resulting mixture over a triple roll mill and the like.
The ceramic powder particles react with one another to undergo shrinkage during sintering in the process of producing such stacked ceramic capacitor, and thus the ceramic portion is densified. The metal powders contained in the conductive paste applied to the sheets also undergo shrinkage during the sintering to form internal electrodes. Since no chemical bond can be formed between the ceramics and metals, however, adhesion between the ceramics and the internal electrodes is so weak that the internal electrodes separate from the ceramic portions (delamination) due to the difference in the level of sintering shrinkage or of thermal expansion coefficient in the ceramics and that of the metals contained in the internal electrode, and that cracking occurs due to the internal stress in the ceramic portions.